Note: Descriptions are shown in the official language in which they were submitted.
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A CLUTCH SYSTEM
FIELD OF INVENTION
The present invention relates to a clutch system having a
pressure plate in bearing contact with a spring diaphragm.
More particularly, the present invention relates to a
modified bearing forming the bearing contact between the
pressure plate and the spring diaphragm.
BACKGROUND OF THE INVENTION
In the typical automotive clutch, the clutch disc is
supported between a pressure plate and the flywheel. A
clutch housing cover which is attached to the flywheel
surrounds the pressure plate and supports a spring
diaphragm, also known as a Bellville diaphragm, which
supplies the clamp load to compress the clutch disc between
the pressure plate and flywheel when the clutch is engaged.
The diaphragm has a fulcrum.support on the clutch housing
cover and the base of the diaphragm rests on a raised
circular rim on the upper surface of the pressure plate.
When the position of the diaphragm is reversed its position
between clutch engagement and disengagement, the base of
the diaphragm rubs against this circular rim, with
frictional losses that cause hysterisis in the clamp load
between engagement and disengagement, and objectionable
wear on the rim of the pressure plate.
The most common diaphragm clutches are the push-off type in
which a force is applied downwardly against the center
fingers of the diaphragm to cause it to move the pressure
plate into a position disengaging the clutch disc. The
need to minimize the size and bulk of automotive components
has led to the development of the pull-off type clutch in
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which a lifting force is applied to the fingers of the
diaphragm to release the pressure plate. In this clutch
design, the base of the diaphragm rests against the
underside of the clutch housing cover, and an annular area
of the diaphragm bears against the raised rim on the
pressure plate.
Qne issue with existing clutch systems, particularly in
those used in racing vehicles is the pedal effort required
to compress the spring diaphragm in order to engage the
clutch. The bearing contact between the spring diaphragm
and the pressure plate is one area where improvements could
be made to reduce the pedal effort.
In the prior art, the Hays patent, US 5,499, 704, is a
continuation-in-part of another Hays patent, US 5,375,688.
The 1688 patent discloses a clutch diaphragm where its base
is supported on a roller, which is either spherical balls
or elongate rollers. Each roller is rotationally supported
on a raised rim of the pressure plate. The rim.retains the
rollers in a circular array of corresponding recesses. In
an alternative embodiment, the elongate rollers are
received in a circular array of elongate recesses. The
elongate recesses may be further modified to retain
cylindrical rollers with a large diameter center tapering
to two smaller diameter ends. While Hays '688 does teach
the use of rotational rollers mounted in the pressure plate
and in bearing contact with the diaphragm, the pressure of
the spring diaphragm applied to the pressure plate of the
bearing contact would prevent any rotation of the roller.
The '704 patent, also issued to Hays, provides for a ball
retainer ring having a plurality of circumferentially
spaced-apart balls, whereby the retainer ring is mounted on
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the upper surface of the pressure plate; the balls provide
fulcrum support for the diaphragm. The improvement of the
1704 patent over the '688 patent relates to ease in
manufacturing a separate retainer ring with stationary
balls for mounting to the pressure plate. However, the
balls are permanently mounted in the retainer ring, and
accordingly are not designed to move within the recess of
the ring.
The British patent, GB 1 432 739, issued to Fichtel & Sachs
AG., discloses a diaphragm spring clutch with reinforcement
points mounted along the periphery of the pressure plate
for supporting the diaphragm. The reinforcements points
are disclosed as either balls (4) or cylindrical pins with
convex end faces, as shown in Figures 1 and 2,
respectively. In a further embodiment, the diaphragm is
also provided with recesses to receive the convex end of
the cylindrical pin in "punctiform contact". The British
patent teaches that the recesses are advantageous in
providing a centering effect for the diaphragm over the
pressure plate. However, the "punctiform contact" provides
a fixed bearing contact where the ball or pin is lodged
inside the recess. The cylindrical pin as taught in the
British patent is transverse with respect to the diaphragm
and pressure plate. Furthermore, the pin is not rotational
when the diaphragm transitions between the engaged and
disengaged states.
The teachings of the first issued Hays patent, and the
British patent, assigned to Fichtel & Sachs, teach a
modified pressure plate as circumferential spaced-apart
arrangement of cylindrical pins, balls, or rollers to form
a bearing contact'with the clutch diaphragm. However,
there is a need in the prior art to provide a further pivot
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for the base end of the spring diaphragm due to the amount
of pressure applied to the balls and rollers by the spring
diaphragm. The amount of pressure applied on the balls or
rollers in conventional clutch systems would prevent any
possible rotation thereof. Therefore, there exists a need
for a bearing that rotates as the spring diaphragm is
shaped for clutch engagement and disengagement.
SUNMARY OF INVENTION
In view of the aforementioned shortcomings of the prior
art, the present invention seeks to provide a modified
pressure plate with circumferentially spaced-apart recesses
that each retain a modified bearing such that it is axially
and rotationally movable. The modified bearings facilitate
the shaping of the spring diaphragm during engagement and
disengagement of the clutch disk.
The present invention seeks to provide a clutch system for
vehicles, particularly racing vehicles, where the amount of
force applied to the pressure plate is critical with
increased engine speed. The present invention is a
modification of the prior art clutch system, and in
particular of the pressure plate in bearing contact with
the spring diaphragm. The prior art pressure plate is
typically formed of an annular ring with a smooth
undersurface, a plurality of angularly spaced bosses for
coupling with the clutch cover, and an upstanding rim on
the upper surface of the plate. The clutch diaphragm is
then mounted below the clutch cover onto the pressure plate
so as to exert an axial force on the clutch disk through
direct contact with the pressure plate when the diaphragm
is flattened for engagement. The axial force applied to
the clutch disk is released when the diaphragm is curved to
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force the pressure plate out of engagement with the clutch
disk.
According to the present invention, the pressure plate has
been modified such that the upper surface provides a
plurality of recesses at circumferentially spaced-apart
locations, preferably in equally radially spaced locations,
to form a circular array. Each recess is dimensioned to
retain a shaft with a rotational bearing for free rotation
and yet also permit axial movement of the rotational
bearing on the shaft. The shaft and rotational bearing
arrangement are in bearing contact with the pressure plate
and the diaphragm. The rotational and axial movement occurs
when the diaphragm is flattened or curved for engagement
and disengagement of the clutch disk, respectively. In
this arrangement, the rotational bearing provides fulcrum
support for the diaphragm when transitioning from a
flattened to a curved shape and vice versa. The rotational
bearing, which may be a spherical ball bearing or needle
bearing for example, is axially movable along the shaft.
The axial movement permits the bearing contact to center
itself on the shaft during the engagement and disengagement
of the clutch disk. By centering the rotational bearing
along the shaft, uniform pressure is applied across the
pressure plate thus increasing the pressure capacity of the
pressure plate. The shaft and bearing arrangement enables
the clutch system to exert greater transfer of force on the
pressure plate than in the prior art clutch systems as
friction loss at the bearing contact is minimized. As
such, the present invention is advantageous for racing
vehicles or high performance vehicles, as well as
transportation and farming vehicles, where the amount of
pressure applied to engage and disengage the clutch system
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is increased due to the increased pressure capacity of the
pressure plate.
The shaft with a bearing that is axially movable within the
recesses of the pressure plate is not disclosed in the
prior art. Moreover, while the prior art teach various
types of bearings, the exact physical structure of the
shaft and rotational bearing as contemplated in the present
invention is not disclosed in any of the prior art relating
to clutch systems.
The present invention is advantageous in that the use of a
rotational bearing helps to reduce the clutch pedal force
required by the user to engage the pressure plate due to
the rotation of the rotational bearing on the shaft.
Furthermore, the present invention is advantageous in that
a more precise fulcrum point of release of the pressure
plate when the spring diaphragm is decompressed. Hence,
the pressure applied to the pressure plate is uniform
across the plate through the centering effect of the
rotational bearing in contact with the diaphragm.
In a first aspect, the present invention provides an
automotive clutch system having a clutch disc supported by
a flywheel and a pressure plate with a spring diaphragm
biased by a release mechanism operating between the
pressure plate and the clutch cover to compress the clutch
disc between the pressure plate and the flywheel in
engagement and to release the clutch disk from the flywhe.el
in disengagement, the pressure plate in bearing contact
with the spring diaphragm, the pressure plate forming a
substantially annular ring with an undersurface to engage
the clutch disk, and an upstanding rim on an upper surface
of the pressure plate, wherein the release mechanism
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comprises: a plurality of shafts and corresponding
rotational bearings as the bearing contact, each shaft and
corresponding rotational bearing arranged such that the
rotational bearing is mounted on the shaft for rotational
movement about the shaft; and the pressure plate having
radially spaced apart recesses in the upper surface of the
pressure plate for retaining each shaft and corresponding
rotational bearing for free rotation about the shaft, the
rotational bearing and the pressure plate being vertically
displaced as the spring diaphragm is shaped for engagement
and disengagement of the clutch disk.
In a second aspect, the present invention provides an
automotive clutch system having a clutch disc supported by
a flywheel and a pressure plate with a spring diaphragm
biased by a release mechanism operating between the
pressure plate and the clutch cover to compress the clutch
disc between the pressure plate and the flywheel in
engagement and to release the clutch disk from the flywheel
in disengagement, the pressure plate forming a
substantially annular ring with an undersurface that
engages the clutch disk, and the pressure plat'e having an
upstanding rim on an upper surface of the pressure plate,
the spring diaphragm being shaped for engagement and
disengagement, the pressure plate in bearing contact with a
base end of the spring diaphragm such that the spring
diaphragm is shaped for engagement to transfer a force
through the release mechanism to the pressure plate to
engage the clutch disk, and when shaped for disengagement,
releases the transfer of force to the pressure plate via
the release mechanism, wherein the release mechanism
comprises: a fulcrum support extending from the clutch
cover and operatively coupled to a diaphragm spring such
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that the base end of the spring diaphragm is movable from
the fulcrum support to displace the pressure plate; a
plurality of shafts and corresponding rotational bearings
as the bearing contact, each shaft and corresponding
rotational bearing arranged such that the bearing is
mounted on the shaft for rotational movement about the
shaft; and the upstanding rim of the pressure plate
defining radially spaced apart recesses in the upper
surface of the pressure plate for retaining the each shaft
and corresponding rotational bearing for free rotation
about the shaft.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will now be described with reference
to the drawings in which:
FIGURE 1 is an elevational sectional view of a typical
push-off type automotive clutch of the prior art;
FIGURE 2 is a plan view of the area of the upper surface of
the pressure plate of an automotive clutch of the prior
art;
FIGURE 3 is an enlarged view of the area within the box
marked 3-3 of FIGURE 2 of the prior art;
FIGURE 4 is a plan view of the area of the upper surface of
the pressure plate of an automotive clutch of the prior art
utilizing elongate rollers;
FIGURE 5 is an enlarged view of the area within the box
marked 5-5 of FIGURE 4;
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FIGURE 6 is a side sectional view of the clutch system in
disengagement according to a first embodiment of the
present invention;
FIGURE 7 is a side sectional view of the clutch system in
engagement according to the first embodiment of the present
invention;
FIGURE 8 is an exploded view of the bearing contact of
FIGURE 6 illustrating movement of the bearing contact in a
clockwise direction relative to the spring diaphragm;
FIGURE 9 is a partial cross sectional view of a shaft and
rotational bearing of the first embodiment of the present
invention;
FIGURE 10 is a cross sectional view of the shaft rotational
bearing taken along line 10-10 of FIGURE 9;
FIGURE 11 is a cross sectional of view of the shaft and
rotational bearing taken along line 11-11 of FIGURE 9;
FIGURE 12 is a plan view of a modified pressure plate
according to a second embodiment of the present invention;
FIGURE 13 is a side sectional view of the modified pressure
plate taken along line 13-13 of FIGURE 12;
FIGURE 14 is a plan view of a modified pressure plate
according to a third embodiment of the present invention;
FIGURE 15 is a side sectional view of the modified pressure
plate taken along line 15-15 of FIGURE 14;
FIGURE 16 is a plan view of a modified pressure plate
according to a fourth embodiment of the present invention;
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FIGURE 17 is a side sectional view of the modified pressure
plate taken along line 17-17 of FIGURE 16; and
FIGURE 18 is a partial cross-sectional view of a shaft and
rotational bearing of a fifth embodiment of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
The invention will be described for the purposes of
illustration only in connection with certain embodiments.
However, it is to be understood that other objects and
advantages of the present invention will be made apparent
by the following description of the drawings according to
the present invention. While a preferred embodiment is
disclosed, this is not intended to be limiting. Rather, the
general principles set forth herein are considered to be
merely illustrative of the scope of the present invention
and it is to be further understood that numerous changes
may be made without straying from the scope of the present
invention.
FIGURE 1 of the prior art shows a sectional view of a
conventional automotive clutch. The clutch is mounted on a
flywheel 10 with a clutch cover 12 that surrounds the
assembly and which is fastened to the flywheel by
conventional machine screws 11. The clutch assembly is
oriented on the center line 13 of the flywheel 10. A
clutch disc 14 is located between the flywheel 10 and the
pressure plate 16. Frictional facings 18 and 20 are
provided on opposite sides of the clutch disc 14 and engage
surfaces on the flywheel 10 and the pressure plate 16. The
pressure plate 16 has a raised annular rim 24 on its upper
surface 26 which provides a support for the base 28 of the
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diaphragm 30. The diaphragm 30 is a Bellville conical
spring diaphragm which has a plurality of radial slots 32,
forming a plurality of fingers. The diaphragm 30 has a
fulcrum support 34 on the undersurface of the clutch
housing cover 12 which is formed by a pair of rings 36 and
38 which are located above and below the diaphragm 30 and
supported by a metal fastener 40 that extends through the
housing cover 12. The arrow 23 indicates the direction of
the release force to disengage the clutch, hence the name
"throw-in" clutch, or pull-off type clutch.
FIGURE 1 of the prior art also shows a ball retainer 56
which is a ring having a plurality of spaced apart
apertures which receive the balls 44 as shown in FIGURE 2.
When the balls 44 are seated in individual spherical
recesses, rather than in a circular groove, the ring 56 is
not necessary. When the balls are seated in a circular
groove such as groove 50 and 52, the retainer ring is quite
useful in retaining the balls 44 at their initial spacings.
The ring rests on the upper edge 46 of the raised circular
rim 24 and insures that the balls remain at the preset
incremental angular spacing.
Referring to FIGURES 2 and 3 of the prior art, the
arrangement of the balls in the innermost circular groove
50 of the pressure plate 16 is illustrated. In the
illustration, the balls 44 are located at equally spaced
apart angular increments. As previously mentioned, the
ball-s can be retained at equal angular spacings by various
retainer means, such as the retainer ring 56, as shown in
FIGURE 1 of 'the prior art. For clarity of illustration,
the retainer ring 56 is not illustrated in FIGURES 2 and 3.
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In this prior art application the upper edge 46 of the
raised circular rim 24 is provided with a plurality of
cylindrical walled recesses 58 at equal angular increments.
An outer circular array 60 of recesses 58, and an inner
circular array 62 of recesses 58 can be provided. The
recesses are elongated and have cylindrical side walls 64,
as shown in FIGURE 5, to receive rollers 66, which are
placed in each recess of either the inner circular array 62
or the outer circular array 60.
Preferably the rollers are right cylindrical rollers, as
illustrated in FIGURES 4 and 5 of the prior art. According
to the prior art, the rollers can also have a large
diameter center 68 and tapering to smaller diameter ends
70. These surfaces are taught as conical, or can be
curvilinear as required.
Referring now to the present invention, FIGURE 6 is a side
sectional view of the clutch system 100 in disengagement
according to a first embodiment of the present invention.
While not all elements required to operate the clutch
system 100 are shown, it is assumed that the skilled
artisan is knowledgeable in that regard. In FIGURE 6, the clutch system 100
shown includes a clutch cover 12, a
pressure plate 16 with an annular ring 24, a spring
diaphragm 30, and the shaft and rotational bearing
arrangement 110 of the present invention. The shaft and
rotational bearing form a bearing contact between the base
of the spring diaphragm and the annular ring 24 of the
pressure plate 16. As discussed earlier with reference to
the prior art, to engage the clutch system 100 such that
the spring diaphragm 30 acts as "a first class lever". The
fulcrum support 34, forming part of the clutch cover 12,
acts a pivot point and lies between an inner end of the
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diaphragm where force is applied to generally flatten the
diaphragm and the base 28 of the diaphragm 34 where the a
load is moved. The fulcrum support 34 includes a rivet 35
for coupling the cover 12 to the diaphragm 30. The load is
effectively the shaft and rotational bearing arrangement
110 and pressure plate 16 which are displaced such that the
pressure plate 16 disengages the clutch disk (not shown).
The arrow 25 indicates the direction of the force to engage
the clutch system.
FIGURE 7 is a side sectional view of the clutch system in
engagement according to the first embodiment of the present
invention. To disengage the clutch system, a release
force indicated by arrow 23 is shown. As force is applied
to the diaphragm at its inner end, the diaphragm is
generally shaped into a slight curve with the inner end
moving close to the pressure plate 16. The upward movement
of the base 28 of the diaphragm toward the clutch cover 12
permits the pressure plate to disengage from the clutch
disk (not shown).
FIGURE 8 is an exploded view of the shaft and rotational
bearing arrangement 110 forming bearing contact of FIGURE
6. The shaft and rotational bearing arrangement 110
comprises a shaft 115 and rotational bearing 120. As is
understood by the skilled artisan, the rotational bearing
120 further comprises rollers 120A and a bearing cage 120B
for permitting the rotation of the rotational bearing 120
about the shaft 115. FIGURE 8 illustrates the displacement
X of the rotational bearing 120 in a clockwise direction
relative to the shaft 115. This is an important aspect of
the present invention in that the displacement of the
rotational bearing reduces the amount of clutch pedal force
required by the user to push the diaphragm for
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disengagement of the clutch disk, as well as the amount of
pressure applied to the pressure plate.
It should be readily understood by the skilled artisan how
the clutch pedal force relates to the force required to
push the diaphragm.
FIGURE 9 is a partial cross sectional view of the shaft and
the rotational bearing of a first embodiment of the present
invention. The rotational bearing shown is also known in
the art, as a needle bearing. The rotational bearing 120
and the shaft 115 may be any suitable dimension provided
the corresponding recess formed in the pressure plate is
dimensioned to retain the rotational bearing 120 and the
shaft 115. The rotational bearing 120 is mounted on the
shaft 115 for rotational movement 115. A further
embodiment of the present invention is dimensioning the
corresponding recess in the pressure plate (shown in FIGURE
12) to permit axial movement along the shaft. The axial
movement of the rotational bearing enables the rotational
bearing to center itself as pressure is applied at the
bearing contact by the spring diaphragm. The centering of
rotational bearing ensures that a uniform pressure is
applied to the pressure plate.
FIGURE 10 is a cross sectional view of the shaft 115 and
the rotational bearing 120 taken along line 10-10 of
FIGURE 9. FIGURE 11 is a further cross sectional of view
of the shaft 115 and the rotational bearing 120 taken along
line 11-11 of FIGURE 9.
FIGURE 12 is a plan view of a pressure plate 24 with a
modified annular rim 24A according to a second embodiment
of the present invention. FIGURE 13 is a side sectional
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view of the modified pressure plate 24 taken along line 8B-
8B of FIGURE 12. The modified annular rim has a plurality
recesses 130A, 130B,..., 130E, for each corresponding shaft
and rotational bearing, as shown in FIGURE 9. Each of the
plurality of recesses 130A, 130B,..., 130E define a
longitudinal axis 131A, 131B,..., 131E that is tangential to
the outer circumference of the annular ring 24A. Each
recess 130A, 130B,..., 130E may be further dimensioned to
permit axial movement of the rotational bearing (not shown)
along its respective longitudinal axis 131A, 131B,..., 131E.
For example, the corresponding rotational bearing (not
shown) for recess 130A has a longitudinal length Y and the
bearing portion of the recess 130A has a longitudinal
length of Z, thus permitting axial movement of the
rotational bearing along the corresponding shaft (not
shown ) .
The rotational and axial movements occur when the diaphragm
(as shown in FIGURES 7, 8) is flattened or curved for
disengagement and engagement of the clutch disk,
respectively. The axial movement permits each bearing to
center itself on the shaft during the engagement and
disengagement of the clutch disk, thus increasing the
pressure capacity of the pressure plate. In this
arrangement, the rotational bearing and the pressure plate
depressed by the diaphragm when transitioning from a
flattened to a curved shape and vice versa.
While each recess of FIGURE 12 is shown as having the same
dimensions, the length of the recess for each shaft and
each rotational bearing along the longitudinal axis 131A,
131B,..., 131E, may vary between the five recesses 130A,
130B,..., 130E,. However, as the pressure applied at the
bearing contact should be uniform across the pressure
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plate, the circumferential dimensions of each shaft and
each rotational bearing should be the same.
The pressure plate 16 further provides a cavity 135 for
clearing rivets when the clutch system is engaged as shown
in.FIGURE 6 as element 35. While the pressure plate of the
present invention does not require a cavity, it may be
included as an additional feature.
FIGURE 14 is a plan view of a pressure plate 16 with a
modified annular rim 24B according to a third embodiment of
the present invention. The annular rim 24B defines a
plurality of recesses 140A, 140B,..., 1401.
FIGURE 15 is a side sectional view of the pressure plate 16
taken along line 15-15 of FIGURE 14, showing two recesses
1401 and 140D.
FIGURE 16 is a plan view of a modified pressure plate with
a plurality of shafts and corresponding rotational bearings
according to a fourth embodiment of the present invention.
In FIGURE 16, the annular rim provides a plurality of
recesses 150A, 150B,..., 1500, that are in close proximity.
The edge of each recess forms an edge of the recess
contiguously disposed beside the recess, i.e. a shaft
portion of recess 150A edges with a shaft portion of recess
150B.
FIGURE 17 is a side sectional view of the pressure plate 16
with a modified annular rim 24C taken along line 17-17 of
FIGURE 16, showing two recesses 150A and 150F.
While the pressure plate 16 shown in FIGURES 12 through 17
each have an annular rim 24A, 24B, 24C, with an odd number
of recesses, the present inVention may be contemplated with
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an even number of recesses and corresponding shafts and
rotational bearings. The present invention is also not
limited to a number of bearing contacts formed between the
spring diaphragm and the pressure plate, i.e., there may be
fewer or more recesses than shown in FIGURES 12 through 17,
provided the dimensions of the recesses and corresponding
shafts and rotational bearings are also adjusted.
FIGURE 18 is a partial cross-sectional view of a shaft and
rotational bearing arrangement using a spherical ball
bearing 200. The spherical ball bearing 200 consists of a
plurality of spherical balls 200A and a spherical ball
bearing cage 200B surrounding the balls.
According to the present invention, the shaft and bearing
arrangement can be made of but not limited to any of the
following: cast steel, carbon steel, brass, brass
impregnated with oil, or a steel alloy. The manufacturing
processes may include a digitized milling machine of the
CNC variety for accurate machining of the raw material.
Any type of pressure plate utilized in a clutch cover
assembly may be modified according to the present
invention. By using pressure plates of the prior art, high
precision machining of those plates would likely avoid an
increase in manufacturing defects typical of any new
component manufacturing process.
It should be understood that the preferred embodiments
mentioned here are merely illustrative of the present
invention. Numerous variations in design and use of the
present invention may be contemplated in view of the
following claims without straying from the intended scope
and field of the invention herein disclosed.
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